1. Field of the Invention
This invention relates to the novel dual functional stabilizer compounds, polymeric compositions and methods for the enhancement in the useful life of plastic materials. More specifically, the subject invention is directed to a novel group of esters which possess multiple functional groups including at least one hindered phenol and at least one hindered amine. These esters are highly effective in the stabilization of plastic composition against the degradative forces of ultraviolet light and the oxygen present in the environment.
2. Description of the Prior Art
The increasing use of polymers in the place of the more traditional types of structural materials, (e.g. wood, metals, etc.) has necessitated the compounding of such polymers with a variety of stabilizers in order to enhance their ability to withstand prolonged exposure to a variety of degradative forces. Degradation of such environmentally sensitive polymers can be caused by exposure to light, heat and/or air. Such degradation is usually manifest by either a partial or total loss of structural integrity, changes in light transmission properties, changes in color, loss or reduction in flexibility and/or resiliency, or any combination of the above phenomenon. As will be appreciated, the stabilizers which are used in conjunction with the above polymeric materials, in addition to providing protection against such degradative forces, must also be compatible with the aesthetic properties of the polymeric article formed from such materials and be effective at low concentrations. The economics of the marketplace dictate that these stabilizers be relatively inexpensive and capable of preparation from readily available starting materials by simple and straightforward synthesis techniques.
The prior art is replete with both patents and technical articles describing various stabilizers suitable for use in structural/engineering plastics and in various synthetic fibers. The hindered amine stabilizers are prominently mentioned as suitable in the stabilization of such materials against ultraviolet light degradation. Illustrative of these hindered amines are the decahydroquinolines disclosed in U.S. Pat. Nos. 3,919,234; 3,920,659; 3,928,330; 4,069,195; and 4,073,770; the 1,5-diazacycloalkan-2-ones disclosed in U.S. Pat. No. 4,207,228; and, the 1,4-diazacycloalkan-2-ones disclosed in U.S. Pat. Nos. 4,167,512 and 4,240,961. These hindered amine stabilizers can be prepared in various ways and from various materials.
The prior art also contains a number of disclosures relating to the thermal stabilization of plastics with various phenolic compounds. A number of these phenolic compounds can be described as sterically hindered, (i.e., have substituents pendant from the phenyl nucleus adjacent to hydroxy substituent). Typically such hindered phenolic antioxidants are only suitable for the inhibition of oxidation of plastics and are used in conjunction with other stabilizers (i.e., UV stabilizers). Representative of the patent literature relating to phenolic antioxidants are U.S. Pat. Nos. 3,330,859 and 3,627,725 (phenolic functional esters); U.S. Pat. Nos. 3,706,740, 3,567,724 and 3,694,440 (phenolic functional triazines); and U.S. Pat. Nos. 3,531,483 and 3,678,047 (phenolic functional isocyanurates).
It is not unusual for a number of the ultraviolet light stabilizers and antioxidants referred to hereinabove to be bimodal in their activity; that is, possess a primary activity for inhibition of degradation from one type of degradative force or agent and a lesser degree of activity for inhibition of degradation from a different type of source or agent. Typical of such compounds are those disclosed in U.S. Pat. No. 3,678,047; which include within its scope the commercial product Goodrite.RTM. 3125 (available from The BFGoodrich Company, Akron, Ohio). Goodrite.RTM. 3125 is sold primarily as an antioxidant although it does also exhibit a lesser degree of effectiveness in the inhibition of ultraviolet degradation. In practice, Goodrite.RTM. 3125 is used in combination with a UV stabilizer such as CYASORB.RTM. 531 (available from The American Cyanamide Company, Wayne, N.J.).
As is readily appreciated by the prior art relating to polymer stabilization, a compound's activity cannot be readily predicted from its structure. Such unpredictability pertains not only to compounds where a single, or principal activity is anticipated, but to compounds which one would anticipate to possess bimodal activity. For example, the compounds disclosed in U.S. Pat. No. 3,919,234 are prepared by alkylation of a piperazine dione with a 2,6-dialkylsubstituted hydroxyphenylaklyhalide. The resultant compound thus obtained has a functional substituent containing a hindered phenol. Yet, such compounds reportedly are only principally effective as UV stabilizers and must be used in conjunction with antioxidants if thermal oxidation of a stabilized resin is to be prevented.
The use of more than one stabilizer in a resin compound is not at all an uncommon practice, however, such practice does increase the cost of the resin and may introduce processing problems and alteration of the resins' physical properties and aesthetic characteristics.
It would, thus, be highly desirable to be able to stabilize a polymeric resin against degradation using the minimum number of ingredients at the lowest possible concentration.